LauBelleSymNR.cc

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// Copyright University of Warwick 2004 - 2013.
// Distributed under the Boost Software License, Version 1.0.
// (See accompanying file LICENSE_1_0.txt or copy at http://www.boost.org/LICENSE_1_0.txt)

// Authors:
// Thomas Latham
// John Back
// Paul Harrison

#include <iostream>

#include "TMath.h"

#include "LauBelleSymNR.hh"
#include "LauDaughters.hh"
#include "LauKinematics.hh"

ClassImp(LauBelleSymNR)


LauBelleSymNR::LauBelleSymNR(const TString& resName, const LauAbsResonance::LauResonanceModel resType,
                             const Double_t resMass, const Double_t resWidth, const Int_t resSpin,
                             const Int_t resCharge, const Int_t resPairAmpInt, const LauDaughters* daughters) :
        LauAbsResonance(resName, resMass, resWidth, resSpin, resCharge, resPairAmpInt, daughters),
        alpha_(0.0),
        model_(resType)
{
}

LauBelleSymNR::~LauBelleSymNR()
{
}

void LauBelleSymNR::initialise()
{
        const LauDaughters* daughters = this->getDaughters();
        Int_t resPairAmpInt = this->getPairInt();
        if ( ! daughters->gotSymmetricalDP() ) {
                std::cerr << "WARNING in LauBelleSymNR::initialise : Dalitz plot is symmetric - this lineshape is not appropriate." << std::endl;
        }
        if ( resPairAmpInt == 3 ) {
                std::cerr << "WARNING in LauBelleSymNR::initialise : This lineshape is intended to be on the symmetrised axes of the DP." << std::endl;
        }

        if ( model_ != LauAbsResonance::BelleSymNR && model_ != LauAbsResonance::TaylorNR ) {
                std::cerr << "WARNING in LauBelleSymNR::initialise : Unknown model requested, defaulting to exponential." << std::endl;
                model_ = LauAbsResonance::BelleSymNR;
        }
}

LauComplex LauBelleSymNR::amplitude(const LauKinematics* kinematics)
{
        // This function returns the complex dynamical amplitude for a Belle Non-Resonant distribution

        // Calculate for symmetric DPs, e.g. 3pi or 3K, by using shapeNo = 1 or 2
        // Have s<->t symmetry already done in Dynamics flip function.
        // For Kpipi or similar plots, one can use the separate exponentials
        // and consider them as two separate components with their own mag and phase.
        // For this shapeNo = 3 and shapeNo = 4 need to be used to create the two
        // individual amplitudes (with the same value of alpha).

        // Calculate Mandelstam variables.
        // s = m_13^2, t = m_23^2, u = m_12^2. 
        Double_t s = kinematics->getm13Sq();
        Double_t t = kinematics->getm23Sq();
        //Double_t u = kinematics->getm12Sq();

        Double_t magnitude(1.0);

        if ( model_ == LauAbsResonance::BelleSymNR ) {
                magnitude = TMath::Exp(-alpha_*s) + TMath::Exp(-alpha_*t);
        } else if ( model_ == LauAbsResonance::TaylorNR ) {
                Double_t mParentSq = kinematics->getmParentSq();
                magnitude = alpha_*(s + t)/mParentSq + 1.0;
        }

        LauComplex resAmplitude(magnitude, 0.0);

        return resAmplitude;
}

LauComplex LauBelleSymNR::resAmp(Double_t mass, Double_t spinTerm)
{
        std::cerr << "ERROR in LauBelleSymNR : This method should never be called." << std::endl;
        std::cerr << "                       : Returning zero amplitude for mass = " << mass << " and spinTerm = " << spinTerm << "." << std::endl;
        return LauComplex(0.0, 0.0);
}

void LauBelleSymNR::setResonanceParameter(const TString& name, const Double_t value) 
{
        // Set various parameters for the lineshape
        if (name == "alpha") {
                this->setAlpha(value);
                std::cout << "INFO in LauBelleSymNR::setResonanceParameter : Setting parameter alpha = " << this->getAlpha() << std::endl;
        } else {
                std::cerr << "WARNING in LauBelleSymNR::setResonanceParameter : Parameter name not reconised.  No parameter changes made." << std::endl;
        }
}